Respiratory System Practice Questions

Q: Curve A signifies which of the following?

Emphysema. ***Emphysema*** - Curve A shows a **leftward and upward shift** on the pressure-volume diagram, indicating **increased lung compliance** where lungs achieve higher volumes at lower pressures. - Characteristic of **emphysema** due to **destruction of alveolar walls** and **loss of elastic recoil**, making lungs easier to inflate but difficult to deflate. *Normal* - Represents the **baseline pressure-volume curve** with normal lung compliance and elastic recoil properties. - Shows typical relationship between **transpulmonary pressure** and lung volume in healthy lungs. *Pulmonary fibrosis* - Would demonstrate a **rightward shift** on the pressure-volume curve, indicating **decreased lung compliance** (stiffer lungs). - Characterized by **excessive collagen deposition** making lungs harder to inflate, requiring higher pressures for same volume. *Asthma* - Shows **near-normal static compliance** unlike emphysema because **elastic tissue remains intact**. - Primary pathology involves **airway hyperresponsiveness** and **bronchoconstriction**, not loss of lung elasticity.

Q: Consider the following statements regarding respiratory function in old age: I. There is increasing ventilation-perfusion mismatch II. There is increased ventilatory response to hypoxia and hypercapnia III. There is a decline in maximum oxygen uptake leading to reduction in cardiorespiratory reserve IV. There is decline in the Forced Expiratory Volume to Forced Vital Capacity ratio (FEV1/FVC) by around 0.2% per year after the forties Which of the statements given above are correct?

I, III and IV. ***I, III and IV*** - With aging, there is a **loss of elastic recoil** in the lungs and a structural decrease in **alveolar surface area**, leading to increased **ventilation-perfusion (V/Q) mismatch** as gravity-dependent areas collapse. - The **maximum oxygen uptake (VO2 max)** declines with age due to reduced cardiac output and skeletal muscle mass, thus decreasing **cardiorespiratory reserve**. The **FEV1/FVC ratio** also decreases by approximately **0.2% per year** after age 40 because of reduced elastic recoil and increased airway collapsibility. *I, II and IV* - While statement I and IV are correct, statement II is incorrect because the **ventilatory response to hypoxia and hypercapnia** actually **decreases** with age. - Older adults have a blunted response to changes in oxygen and carbon dioxide levels, making them more susceptible to respiratory compromise. *II, III and IV* - Statement II is incorrect as the **ventilatory response to hypoxia and hypercapnia decreases** with age, not increases. - Statements III and IV accurately describe the decline in **maximum oxygen uptake** and the **FEV1/FVC ratio** with aging. *I, II and III* - Statement II is incorrect; the **ventilatory response to hypoxia and hypercapnia is diminished** in older adults. - Statements I and III correctly identify increased **ventilation-perfusion mismatch** and decreased **maximum oxygen uptake** as age-related changes in respiratory function.

Q: Which of the following are the functions of larynx ? 1. Fixation of the chest 2. Aids in swallowing of food 3. Phonation 4. Respiration Select the correct answer using the code given below :

All of the above (1, 2, 3 and 4). ***All of the above (1, 2, 3 and 4)*** - The larynx performs **all four functions** listed in the question. - **Respiration**: The larynx serves as a vital conduit for airflow. The posterior cricoarytenoid muscles actively abduct the vocal cords during inspiration, and the larynx regulates airflow through glottic opening and closure. - **Phonation**: The vocal cords housed within the larynx vibrate to produce sound, making this the primary organ of voice production. - **Aids in swallowing**: During deglutition, the larynx elevates and the epiglottis closes the laryngeal inlet to prevent aspiration of food into the trachea. - **Chest fixation**: The larynx closes the glottis during the Valsalva maneuver, creating a closed air column that stabilizes the chest for activities like lifting, coughing, defecation, and parturition. *1, 2 and 3* - This option incorrectly excludes **respiration**, which is a fundamental function of the larynx as part of the conducting airways. - The larynx is not merely a passive tube but actively regulates airflow through intrinsic muscle activity. *2, 3 and 4* - While these are all valid laryngeal functions, this option incorrectly excludes **chest fixation**, which is accomplished through glottic closure during the Valsalva maneuver. *1, 3 and 4* - This option incorrectly excludes the larynx's role in **aiding swallowing** through laryngeal elevation and airway protection during deglutition.

Q: O2 (Oxygen) dissociation curve is shifted to right in the following except

Metabolic alkalosis. ***Metabolic alkalosis*** - A shift to the **right** on the oxygen dissociation curve indicates **decreased affinity** for oxygen, promoting oxygen release to tissues. - In **metabolic alkalosis**, the blood pH is elevated, which **increases hemoglobin's affinity for oxygen**, leading to a **left shift** in the curve. *Hypercapnia* - **Hypercapnia** (increased PCO2) decreases blood pH, reducing hemoglobin's affinity for oxygen via the **Bohr effect**, resulting in a **right shift**. - This facilitates oxygen release to tissues where CO2 production is high. *Rise in temperature* - An increase in **body temperature** weakens the binding of oxygen to hemoglobin, causing a **right shift** in the oxygen dissociation curve. - This is beneficial during exercise, when active tissues generate heat and require more oxygen. *Raised 2, 3 DPG level* - **2,3-bisphosphoglycerate (2,3-BPG)** binds to deoxygenated hemoglobin, stabilizing its T-state and **reducing its affinity for oxygen**, causing a **right shift**. - This is a key adaptation to chronic hypoxia, enhancing oxygen delivery to tissues.

Q: CO poisoning causes which type of hypoxia?

Anemic hypoxia. ***Anemic hypoxia*** - **Carbon monoxide (CO)** binds to **hemoglobin** with an affinity much higher than oxygen, forming **carboxyhemoglobin**. - This effectively reduces the **oxygen-carrying capacity of the blood**, mimicking a severe anemia, despite normal arterial PO2. *Hypoxic hypoxia* - Occurs when there is **insufficient oxygen delivery to the blood** due to low arterial PO2, as seen in high altitudes or respiratory diseases. - In CO poisoning, **arterial PO2 is typically normal**, distinguishing it from hypoxic hypoxia. *Stagnant hypoxia* - Results from **inadequate blood flow** to tissues, leading to reduced oxygen delivery, as observed in heart failure or shock. - CO poisoning primarily affects oxygen transport by hemoglobin, not the **rate of blood flow**. *Histotoxic hypoxia* - Characterized by the **inability of tissues to utilize oxygen** effectively, even when oxygen delivery is adequate, as seen in cyanide poisoning inhibiting cytochrome oxidase. - In CO poisoning, tissues can utilize oxygen; the problem is the **reduced availability of oxygen** from hemoglobin.

Q: What does zero pressure indicate in the pressure-volume curve?

Functional residual capacity. ***Functional residual capacity*** - This is the lung volume at which the **elastic recoil of the lungs** exactly balances the **elastic recoil of the chest wall**, resulting in zero net pressure across the respiratory system. - At **functional residual capacity (FRC)**, there is no airflow, and the **alveolar pressure equals atmospheric pressure (zero)**, indicating the equilibrium point. - Note: The **transpulmonary pressure remains positive** at FRC (approximately +5 cm H₂O), which keeps the lungs inflated against their elastic recoil. *Inspiratory reserve volume* - This is the **extra volume of air** that can be forcibly inhaled after a normal inspiration. - It involves active inspiration and therefore is associated with a **negative intrathoracic pressure**, not zero pressure. *Tidal volume* - This is the **volume of air inhaled and exhaled** during a normal quiet breathing cycle. - While breathing, pressures fluctuate, and the respiratory system is not at an equilibrium point of **zero pressure** throughout the tidal breath. *Residual volume* - This is the **volume of air remaining in the lungs** after a maximal exhalation. - The chest wall's outward recoil is greater than the lung's inward recoil at this point, resulting in a **negative intrapleural pressure** to keep the lungs from collapsing.

Q: Identify the pathology from the given flow-volume loop:

Fixed central airway obstruction. ***Fixed central airway obstruction*** - This flow-volume loop shows **flattening of both the inspiratory and expiratory limbs**, creating a characteristic "box" or "square" shape. - This pattern indicates that airflow is limited equally during both inspiration and expiration, regardless of lung volume changes, which is characteristic of a **fixed central airway obstruction**. - Examples include **tracheal stenosis, tracheal tumors, or fixed goiters** compressing the trachea. *Variable extrathoracic obstruction* - Characterized by flattening of the **inspiratory limb only**, as negative intrathoracic pressure during inspiration exacerbates the obstruction. - The expiratory limb typically remains normal as positive intrathoracic pressure tends to open the airway. - Examples include **vocal cord paralysis or extrathoracic tracheal tumors**. *Variable intrathoracic obstruction* - Characterized by flattening of the **expiratory limb only**, as positive intrathoracic pressure during forced expiration collapses the airway. - The inspiratory limb usually remains normal as negative pressure helps maintain airway patency. - Examples include **intrathoracic tracheal tumors or tracheomalacia**. *Fixed distal airway obstruction* - Fixed obstructions producing the characteristic "box" pattern are typically **central (proximal) lesions in large airways**, not distal. - Distal airway obstructions (like **COPD or asthma**) produce a different flow-volume loop pattern characterized by **decreased peak expiratory flow** and "scooping" or "concave" appearance of the expiratory limb, not the flat bilateral pattern seen here.

Q: Which among the following has the highest airway resistance?

Bronchi. ***Bronchi (Medium-sized bronchi)*** - The **medium-sized bronchi** (approximately 4th-8th generation airways) contribute the **highest proportion to total airway resistance** in the tracheobronchial tree. - At this level, airways are still relatively **narrow** but arranged more in **series** rather than parallel, concentrating resistance. - This is the point of **maximum resistance** before the extensive branching of smaller airways creates parallel pathways. - Accounts for approximately **40-50% of total airway resistance** during normal breathing. *Small bronchioles* - While individual small bronchioles (<1 mm diameter) have narrow lumens, they branch extensively into **thousands of parallel airways**. - This creates an **enormous total cross-sectional area** (up to 20x larger than trachea), which dramatically **reduces total resistance**. - According to principles of parallel resistance, total resistance decreases as more parallel pathways are added: 1/R_total = 1/R₁ + 1/R₂ + ... + 1/Rₙ - Despite small individual diameter, collective parallel arrangement makes them **low resistance** pathways. *Alveolar ducts* - Have the **largest cumulative cross-sectional area** in the entire respiratory system. - Airflow velocity is minimal and flow is entirely **laminar**, offering negligible resistance. - These are part of the respiratory zone where gas exchange occurs primarily by diffusion. *Respiratory bronchioles* - Part of the **transitional/respiratory zone** with extensive branching and large total cross-sectional area. - Offer very low resistance due to their **parallel arrangement** and slow airflow velocity. - Contribute minimally to total airway resistance.

Q: A histological examination of the carotid body reveals glomus cells containing dense-core vesicles. These cells function primarily as chemoreceptors for which of the following?

Partial pressure of oxygen. ***Partial pressure of oxygen*** - Carotid body **glomus cells** are highly specialized **chemoreceptors** that primarily sense changes in the **partial pressure of oxygen (PO2)** in arterial blood. - When PO2 decreases (e.g., hypoxia), these cells are activated and stimulate the respiratory and cardiovascular systems to increase oxygen uptake. *Blood pH* - While carotid body chemoreceptors can sense large changes in blood pH, their primary and most sensitive role is in detecting changes in **PO2**. - Central chemoreceptors in the brainstem are more crucial for routine regulation of respiration in response to changes in **pH and PCO2**. *Temperature* - **Thermoreceptors** located in the skin, hypothalamus, and other internal organs are responsible for sensing body temperature, not the carotid body. - The carotid body's main function is related to blood gas homeostasis, not temperature regulation. *Blood glucose levels* - Blood glucose levels are regulated by specialized cells in the **pancreas** (islets of Langerhans) that secrete hormones like insulin and glucagon. - The carotid body is not directly involved in sensing or regulating glucose homeostasis.

Q: Which mechanism is primarily responsible for the increase in pulmonary diffusing capacity during exercise?

Pulmonary capillary recruitment. ***Pulmonary capillary recruitment*** - During exercise, more **pulmonary capillaries** that were previously unperfused or poorly perfused open up, increasing the **surface area available for gas exchange**. - This **recruitment** directly enhances the pulmonary diffusing capacity by providing more sites for oxygen to cross from the alveoli into the blood. *Decreased airway resistance* - While airway resistance can decrease during exercise due to **bronchodilation**, this primarily affects **airflow** and ventilation, not the efficiency of gas diffusion across the alveolar-capillary membrane. - Reduced airway resistance facilitates getting air into and out of the lungs but does not expand the surface area for diffusion or thin the membrane. *Reduced membrane thickness* - The thickness of the **alveolar-capillary membrane** is a structural characteristic that does not significantly change acutely during exercise. - While a thinner membrane would improve diffusion, this is not the primary mechanism behind the exercise-induced increase in diffusing capacity. *Increased alveolar ventilation* - Increased alveolar ventilation ensures a higher **partial pressure of oxygen** in the alveoli. - While essential for delivering oxygen, it primarily affects the **driving pressure for diffusion** rather than the physical capacity of the diffusion barrier itself.

Question 1

Curve A signifies which of the following?

Accepted Answer

Emphysema

Answer

Normal

Answer

Pulmonary fibrosis

Answer

Asthma

Question 2

Consider the following statements regarding respiratory function in old age:
I. There is increasing ventilation-perfusion mismatch
II. There is increased ventilatory response to hypoxia and hypercapnia
III. There is a decline in maximum oxygen uptake leading to reduction in cardiorespiratory reserve
IV. There is decline in the Forced Expiratory Volume to Forced Vital Capacity ratio (FEV1/FVC) by around 0.2% per year after the forties
Which of the statements given above are correct?

Accepted Answer

I, III and IV

Answer

I, II and IV

Answer

II, III and IV

Answer

I, II and III

Question 3

Which of the following are the functions of larynx ?

1. Fixation of the chest
2. Aids in swallowing of food
3. Phonation
4. Respiration

Select the correct answer using the code given below :

Accepted Answer

All of the above (1, 2, 3 and 4)

Answer

1, 2 and 3

Answer

2, 3 and 4

Answer

1, 3 and 4

Question 4

O2 (Oxygen) dissociation curve is shifted to right in the following except

Accepted Answer

Metabolic alkalosis

Answer

Hypercapnia

Answer

Rise in temperature

Answer

Raised 2, 3 DPG level

Question 5

CO poisoning causes which type of hypoxia?

Accepted Answer

Anemic hypoxia

Answer

Hypoxic hypoxia

Answer

Stagnant hypoxia

Answer

Histotoxic hypoxia

Question 6

What does zero pressure indicate in the pressure-volume curve?

Accepted Answer

Functional residual capacity

Answer

Inspiratory reserve volume

Answer

Tidal volume

Answer

Residual volume

Question 7

Identify the pathology from the given flow-volume loop:

Accepted Answer

Fixed central airway obstruction

Answer

Variable extra thoracic obstruction

Answer

Variable intrathoracic obstruction

Answer

Fixed distal airway obstruction

Question 8

Which among the following has the highest airway resistance?

Accepted Answer

Bronchi

Answer

Alveolar duct

Answer

Respiratory bronchioles

Answer

Small bronchioles

Question 9

A histological examination of the carotid body reveals glomus cells containing dense-core vesicles. These cells function primarily as chemoreceptors for which of the following?

Accepted Answer

Partial pressure of oxygen

Answer

Blood pH

Answer

Temperature

Answer

Blood glucose levels

Question 10

Which mechanism is primarily responsible for the increase in pulmonary diffusing capacity during exercise?

Accepted Answer

Pulmonary capillary recruitment

Answer

Decreased airway resistance

Answer

Reduced membrane thickness

Answer

Increased alveolar ventilation

Respiratory System — MCQs

Respiratory System — MCQs

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